The present invention relates to a header assembly for mounting to a circuit substrate and for receiving a complementary electrical connector. In particular, the present invention is for a high density header assembly for use in, for example, a motherboard in a backplane/back panel application.
In a typical electrical interconnection system, a first removably insertable circuit board includes a complementary electrical connector that is to be mated with a header assembly or header which is mounted to a second circuit board. As should be understood, when the first circuit board is coupled to the second circuit board by way of the electrical connector and header and when the first circuit board is in operation, a number of signals enter or leave the first circuit board through conductive paths defined by the electrical connector on the first circuit board and the header on the second circuit board. In many instances, the second circuit board has other circuit boards coupled thereto by other respective headers and complementary electrical connectors, and the aforementioned signals can originate from or be destined for such other circuit boards. Of course, the aforementioned signals can also originate from or be destined for other locations remote from the second circuit board by way of appropriate interconnections.
If it is desirable to suppress signal noise and/or crosstalk, it is known that a signal may be transmitted over a pair of differential (positive and negative) signal lines that travel together in close proximity. Typically, in such pair of differential lines, the signal itself (+V) is transmitted on the positive line, and the negation of the signal (xe2x88x92V) is transmitted on the negative line. Since both lines travel together in close proximity, any noise encountered by the lines should appear in a generally identical form on both lines. Accordingly, the subtraction (by appropriate circuitry or other means) of the negative line (xe2x88x92V+noise) from the positive line (+V+noise) should cancel out such noise ((+V+noise)xe2x88x92(xe2x88x92V+noise)=2V), thus leaving the original signal, perhaps with a different amplitude.
Oftentimes, in a high frequency environment, most every signal passing to and from a circuit board travels as a pair of differential signals on a pair of differential signal lines. Accordingly, the electrical connector on the circuit board and the header on the backplane must accommodate all such pairs of differential signal lines. Moreover, with increased contact density on a circuit board, there has been a corresponding increase in signal lines associated with such circuit board. As a result, the number of individual lines running through the electrical connector of the circuit board and the associated header can be quite large. At the same time, since it is desirable to increase the number of circuit boards that can be coupled to the backplane, the xe2x80x98real estatexe2x80x99 on the backplane used by the header must be kept small. Therefore, the xe2x80x98densityxe2x80x99 of individual signals that pass through the electrical connector and header must be increased.
With such increased density, however, the issue of susceptibility to noise and/or crosstalk again arises, even in electrical connectors and headers that transmit pairs of differential signals. To combat such density-based noise, the header in particular has been modified to include ground shielding which substantially electromagnetically isolates within the header each pair of differential signal lines from every other pair of differential signal lines.
Accordingly, a need exists for a header that can have multiple differential signal pairs in relatively high density, and that has ground shielding for the signal pins, where the header is practical and relatively easily manufactured.
The present invention satisfies the aforementioned need by providing a header assembly for being mounted to a circuit substrate such as a backplane and for receiving a complementary electrical connector secured to a daughter-board. The header assembly has an insulating shroud, a plurality of signal pins, a plurality of ground shields, and a plurality of ground pins, all mounted to the base of the shroud.
Such base has a backplane side for facing toward the backplane, a connector side for facing toward the mating connector, and a primary edge. The signal pins are arranged into a plurality of rows extending in a first direction along the base and along the primary edge of the base, and a plurality of columns extending in a second direction along the base generally perpendicular to the first direction. In differentially paired signal pins, such signal pins in each pair are adjacently arranged into a sub-row extending in the first direction. Each signal pin in a pair has an inner side facing toward the other pin in the pair, an outer side opposite the inner side, a primary side extending between the inner side and the outer side and facing toward the primary edge of the base, and a non-primary side extending between the inner side and the outer side and facing away from the primary edge of the base.
One ground shield is associated with each signal pin. Each ground shield generally extends through the base between the connector side and the backplane side, and includes first and second attached wings arranged at about right angles. The first wing extends generally along the first direction adjacent and along one of the primary side and the non-primary side of the associated signal pin, and the second wing extends generally along the second direction adjacent and along the outer side of the associated signal pin. The plurality of ground shields in combination substantially electromagnetically isolate within the base of the shroud each pair of signal pins from every other pair of signal pins. Each ground pin electrically contacts at least one ground shield at the second wing thereof.